Traditionally, consumers have had to choose between the superior durability offered by latex paints and the superior hiding properties of oil-based paint. Conventional latex or emulsion paints require an underlying primer coat prior to their application to provide an adequate level of blocking and to prevent bleed-through, such as of tannins. In addition, many conventional latex paints require a primer coat to provide adequate adhesion and durability for specific applications. Often, even when a primer is applied, multiple coats of the prior art paints are required to prevent an alteration of color due to the presence of the primer or bleed through of dyes and pigments from the underlying substrate. In fact, multiple applications of prior art paint will not prevent bleed-through on substrates such as cedar since the dyes and pigments, such as tannins contained in the substrates, are often water soluble and diffuse through each layer of the latex paint.
Paint typically contains four essential ingredients, namely pigment, binder, liquid and additives. Any or all of these ingredients may be a single component or may comprise multiple items. Pigment provides color to paint and also makes paint opaque, and pigment is usually of mineral or organic origin although some pigments are artificially produced. Some pigments possess little or no bulk and must be fixed on a more solid, but at the same time transparent, substance or base. “Prime” pigments provide color and opacity (opaque coverage). The most common prime pigment is titanium dioxide, which is white and is used in latex and oil-based paints.
Traditionally, pigments have also added hiding properties to paint. Specialty or extender pigments may also be used and provide bulk to the paint at a low cost. The extender pigments are often chosen for their impact on properties like scrub resistance, stain resistance and chalk resistance. Alum or clay are frequently used for this purpose. These pigments are added to the paint to provide certain characteristics such as thickness, a certain level of gloss and durability. They are usually naturally occurring products which originally were in the earth and were mined and purified for use in paint. Such pigments as calcium carbonate, talc and clay are, for example, used extensively in paints.
The binder holds the pigment and also adheres it to a surface, and a binder composition may have more than one component. In latex paint, the latex resin is the binder. Most commonly in latex paint, the binder is 100% acrylic, vinyl acrylic (polyvinyl acetate), or styrenated acrylic. The pigment particles are insoluble and merely form a suspension in the binder. The binder “binds” the pigment into a tough, continuous film and as noted above helps the paint adhere to the surface. In addition, it has been found previously that the use of 100% acrylic binder provides for maximum adhesion when wet and also provides for resistance to blistering and peeling, resistance to mildew and dirt, and alkali resistance for paint applied over fresh masonry.
Liquids carry the pigment and binders, and this liquid is the part of the paint or coatings product which evaporates. The role of the liquid is to keep the paint in a fluid form for ease of application. Once applied to the surface it evaporates leaving a uniform film which then dries to form a protective coating. The liquid used is primarily determined by the solubility of the binder. In oil-based and alkyd paints, the liquid is typically an organic solvent, and in latex paints, the liquid is typically water. Traditionally, top quality paints have less liquid and more solids (i.e. pigment & binders) as measured by percent solid.
Additives are ingredients used at low levels to provide key properties, such as but not limited to: mildew resistance, improved flow and leveling, and spatter resistance. Common additives used in conventional paint formulations include rheology modifiers, surfactants, defoamers, coalescents, and biocides. Other numerous additives are well-known in the art and may be utilized as required to formulate a paint having the desired properties.
Various techniques are known in the art for producing paints having various types of sheens, i.e. “shine” or gloss. For example, by incrementally increasing pigment levels and/or by using larger pigment particles, various gloss levels can be achieved including, but not limited to flat, satin, and semi-gloss. Pigment volume concentration (PVC) is often associated with the paint finish, although various finishes may have overlapping ranges of PVC. PVC is the unit volume of pigments as a percentage of the volume of pigments plus the volume of the binder. PVC represents the relationship between durability of the coating and the amount of pigment.
In addition to the sheens, it is well known in the art to formulate paint compositions to allow for the desired pigment which is added for color. For example, where a near white coating is desired a high volume of TiO2 may be used and a small volume of coloring pigment is necessary. In contrast, where a dark color is preferred in the final coating, a large volume of coloring pigment is needed and a corresponding decrease in the amount of TiO2 is necessary.
Thus, there is a need for a high colorant volume paint composition and method of making the same to replace the traditional role of a primer and topcoat system and which is capable of providing a coating having improved properties such as, tannin blocking, hiding power, stain removal, and corrosion resistance.